This invention applies to a category of self-propelled, climbing vehicles that primarily make use of wheels or endless tracks to provide propulsion along a climbing surface, but could employ legs. More specifically, this invention applies to a vehicle well adapted to climbing non-planar surfaces such as pipes or other structural members while traveling along a single dimension, for example traveling parallel to the axis of the pipe. For this purpose, the term climbing vehicle refers to a vehicle that is capable of traversing a surface horizontally or vertically in some inclined or inverted position relative to the earth horizon. Further, it is intended that the climbing vehicle is able to accommodate irregularity in the climbing surface including convex or concave regions. Such climbing vehicles may be used to conduct remote operations such as inspection, maintenance, or manufacturing in environments that pose difficulty or danger for human operation. These climbing vehicles could also be used in a wide variety of applications including power production, civil structures, or shipbuilding. A variety of climbing vehicles have been proposed to operate in these conditions. The methods of achieving mobility for climbing vehicles include but are not limited to legged locomotion, endless tracks or wheeled devices. Patent literature demonstrating examples of climbing vehicles employing endless tracks include U.S. Pat. No. 3,960,229, U.S. Pat. No. 4,789,037, U.S. Pat. No. 4,828,059, U.S. Pat. No. 5,366,038, U.S. Pat. No. 5,435,405, U.S. Pat. No. 5,487,440, U.S. Pat. No. 5,884,642, U.S. Pat. No. 5,894,901, U.S. Pat. No. 6,889,783, U.S. Pat. No. 7,498,542 B2, U.S. Pat. No. 7,775,312, and US application publication numbers US 2012/0111649 A1, US 2012/0116583 A1, US 2012/0111843 A1. Patent literature demonstrating examples of climbing vehicles employing wheels include U.S. Pat. No. 3,690,393, U.S. Pat. No. 3,810,515, U.S. Pat. No. 4,010,636, U.S. Pat. No. 5,049,218, U.S. Pat. No. 5,355,807, U.S. Pat. No. 5,853,655, U.S. Pat. No. 6,000,484, U.S. Pat. No. 6,564,815, U.S. Pat. No. 6,596,22, U.S. Pat. No. 6,595,152, U.S. Pat. No. 6,627,004 B1 2003, U.S. Pat. No. 6,688,938, U.S. Pat. No. 6,793,026, U.S. Pat. No. 6,886,651, and US application publication numbers US 2009/0078484, U.S. Pat. No. 7,309,464 B2, US 2010/0212983 and US 2010/017610. The majority of the wheeled-type climbing vehicles employ magnets in the wheel portion as demonstrated in U.S. Pat. No. 2,694,164. Advanced features in magnetic wheels have been demonstrated, for example as in U.S. Pat. No. 6,125,955. The use of wheels in climbing platforms provides several advantages, including relative simplicity in their design and actuation, and constant pitch properties that contribute to uniform motion transfer. The primary difficulty in using a wheeled-type platform for climbing is that the wheels require theoretical point contact with the surface to enable efficient rolling. This point contact limits the region in which adhering elements can connect or be in close proximity to the climbing surface. Adhering elements may be made of magnets, suction cups, adhesive or other device that can create an adhering force to the climbing surface. The size of the contact region for adhering members is generally related to the amount of adhering force that can be generated.
The size of the available contact region for wheeled climbing vehicles can be increased by increasing the number of wheels in contact with the climbing surface to yield an increase in the overall adhering force of the vehicle. For example, when magnets are used as adhering members, they may be embedded in the wheel to rotate with the wheel (U.S. Pat. No. 2,694,164), or they may be suspended to the wheel axis but have the ability to move circumferentially about the wheel (U.S. Pat No. 0,212,983). While the overall adhering force of the vehicle can be increased by increasing the number of wheels in contact with the climbing surface, this raises several technical difficulties in the design and implementation of these systems. First, as the number of wheels increases, the complexity of the system increases. Second, as the number of wheels in contact with the climbing surface increases beyond a minimal number, for example three to provide stability when the contact surface is non-planar, wheel suspensions are required to ensure wheel contact with the surface. Third, as the number of wheels in contact with the surface increases, the kinematic requirements for steering increase, or slipping is introduced into the system which decreases efficiency. For these reasons, climbing vehicles with large numbers of wheels that have the adhering members integrated in the wheels are seldom seen in practice.
More commonly, wheeled vehicles that employ adhering members integrated into the wheels employ a reduced or minimal number of wheels in wheel-based climbing systems. This can be seen in several examples in the literature including U.S. Pat. No. 6,627,004, U.S. Pat. No. 6,793,026 and U.S. Pat. No. 7,625,827. These typically employ either three wheels or four wheels. Three wheel systems enjoy the advantage of not requiring any type of suspension to insure contact of each wheel with the climbing surface when climbing on non-planar terrain. Four wheel systems are shown to incorporate a simple suspension design to maintain contact between the wheels and the climbing surface.
When a reduced number of wheels, for example three or four, are employed in a wheel-based climbing system, the forces required for equilibrium directed away from the surface will at times during operation be concentrated on a single wheel and associated adhering member. This concentration of forces on a single wheel results in a reduced payload capacity of the climbing vehicle. The payload capacity of climbing vehicles is one of the primary performance metrics in the design of such a vehicle. Thus, wheel-type climbing robot vehicles that place the adhering members in our about the wheels have limitations in the payload capacity.
Alternatively, the literature of wheel-type climbing robots demonstrates inventions that place the adhering members in the frame or chassis of the vehicle. An example of this is given in U.S. Pat. No. 3,810,515. This type of design is employed in a large number of commercially available climbing platforms. An example of such a commercial product is the Handiweld sold by Bug-O. These devices limit the ability of the adhering member to adapt to the climbing surface, particularly on curved surfaces such as pipes.
The design that places the adhering member directly in the chassis encounters significant performance limitations however when the system is used on a surface that is not flat, or has protrusions or indentions in the surface. This limitation arises from a technical difficulty that the chassis cannot conform to variations in the geometry of the climbing surface, such that the distance between the chassis and surface is changing during operation. The adhering force is typically strongly dependent on this distance, with an increase in distance between the adhering member and the climbing surface generally resulting in a decrease in adhering force. The decreased adhering force limits the available payload, thus limiting the performance of this type of invention.
The invention of this patent provides a novel means to overcome the limitations discussed for wheel-type climbing platforms. This invention provides a means to increase the number or magnitude of adhering force elements without increasing the number of wheels in a wheel-type climbing platform. The invention also provides a means to ensure or maintain a constant distance between the adhering force member and the climbing surface, to maintain the magnitude of adhering force during operation. Further, the invention allows the device to orient itself in a lateral direction to the climbing surface, along a single dimension (defined by the travel direction). Finally, the invention provides a means to distribute the loads required for equilibrium during climbing in an optimal manner over a large number of adhering members, while making sure that all wheel members stay in contact with the climbing surface.
Vehicles designed to traverse non-planar surfaces consisting of an extruded member of generally uniform constant cross section can make use of this uniformity to maintain alignment of the vehicle with the longitudinal axis of the structural member. This allows the vehicle to travel along a single dimension parallel to the dominant axis of the structural member. This reduces the need of the climbing machine to incorporate steering in situations in which it is simply desired to travel along the structural member. This reduces the number of actuators involved in the system and reduces the necessary complexity. Examples of such a system would be in traveling along pipes or along tube sheets formed as a series of tubes lying side by side.
This patent presents a new invention for a climbing vehicle system. This invention places the adhering members (members that create an adhering force to the climbing surface) along a single dimension, the longitudinal axis of the climbing machine. This dimension is called the primary axis. The invention allows this primary axis to be aligned in a preferred manner with the climbing surface, through an auxiliary trailing arm, with a suspension located in the trailing arm. The suspension can take one of three forms; 1) rigid, 2) passive suspension allowing motion as a defined function of force, 3) active suspension controlling both deflection and force in a prescribed manner. This allows the invention to operate on curved surfaces such as small diameter pipes. The primary adhering members (for example magnets) can be rigidly attached to the frame of the vehicle along the primary axis, or located on a suspension member, called a resilient guide, which is attached to the vehicle chassis in a way that allows the resilient guide to move independently of the vehicle chassis to accommodate variations in the geometry of the climbing surface. Furthermore, the resilient guide is able to transfer forces between the chassis and the adhering members in a manner that distributes the loads required for equilibrium among multiple adhering members. The resilient guide can deform to accommodate large variations in the geometry of the climbing surface. This allows the adhering members to maintain a constant distance from the climbing surface to maintain the adhering force. Finally, the invention provides a mechanism by which the resilient guide will be automatically or self-attract to the climbing surface.